Acetylcholine Receptor Ab (ACRA)

Test investigation

Acetylcholine Receptor Ab (ACRA)

Laboratory offering test

Referral laboratory

Units

nmol/L

Also known as/Frequency of test

ACR; ACHR; Myasthenia antibody; Motor end plate antibody; MG antibody, ACRA

Indications

Acetylcholine receptor antibodies are a highly sensitive and specific marker for generalised myasthenia gravis (80-90% sensitivity); up to 90% of generalised MG cases are ACHR positive for ACHR antibodies whilst in pure ocular MG up to 50% of patients are positive Level of antibodies do not correlate with disease activity, so repeated testing is not indicated. In patients with suspected MG who are negative for ACRA, anti-MuSK (muscle-specific receptor tyrosine kinase) antibodies may be indicated.

Comments precautions

Plasma NOT acceptable. Referred outside of EPA

Sample type

Serum

Turnaround times (TAT) Urgent/Routine/GP or OPD

2 weeks

Reference intervals

<0.2nmol/L Negative 0.2 – 0.4 nmol/L Doubtful >0.4nmol/L Positive